A wide variety of products are now packaged for dispensing as a finely divided aerosol spray and many of these products include a major amount of a finely divided powder such as talc, sodium bicarbonate, sodium carbonate, aluminum chlorohydrate, and the like. Products which contain a major amount of a finely divided powder may, for example, include antiperspirants, insecticides, and fire retardant compositions.
As disclosed in my prior copending U.S. patent application Ser. No. 544,390, it is now possible to dispense a fine spray of an aerosol product from a barrier-pack container. In accomplishing this result, a neutral propellant together with a relatively non-foaming liquid product or a finely divided powder product is contained within compressible inner container while means positioned between the inner container and an outer container are provided to compress the inner container means. A mechanical breakup spray head and valve assembly are connected to the inner container means and, during discharge of product, the neutral propellant is at least partially vaporized on passage of the product and neutral gas through the spray head.
By using the aerosol dispensing system described in my prior applications, it is now possible to eliminate a number of problems which have long plagued the aerosol industry. Among these problems are incompatibility of the propellant and product at high propellant-to-product volume ratios such as, for example, in the use of a liquified hydrocarbon propellant with a water base paint or in the use of a halogenated hydrocarbon propellant for a water base product. In my aerosol dispensing system, the product is discharged in conjunction with a relatively small amount of a neutral propellant from a compressible inner container positioned within an outer container. The force required for discharge of the product and neutral propellant in the form of a finely divided spray is provided by compression of the compressible inner container. Since the neutral propellant present in admixture with the product in my aerosol system does not function as a primary propellant (i.e., in generating a driving force to expel the product in the form of a finely divided spray), the quantity of neutral propellant may be maintained at a relatively low level with respect to the quantity of the product. This, then, avoids the compatibility problems which were previously experienced in conventional aerosol systems where the primary propellant and product are not separated and also permits the use of a greater quantity of product in an aerosol dispensing system.
In conventional aerosol dispensing systems, it has sometimes been necessary to employ a very large quantity of propellant to generate a driving force and to sufficiently dilute a relatively small quantity of a viscous product for discharge, such as a frying pan spray. In these prior conventional systems, the use of relatively high propellant-to-product volume ratios may make the aerosol product unattractive to the consumer who must purchase a relatively large quantity of propellant to obtain a relatively small quantity of product. In my aerosol dispensing system, as described in my prior U.S. patent applications, a larger quantity of product may be present since it is no longer necessary to dilute the product with gross quantities of propellant to dispense the product in the form of a fine spray. This provides a savings to the consumer who no longer has to purchase a large quantity of unwanted propellant to obtain a relatively small quantity of desired product in the form of an aerosol spray.
Additionally, in the use of my aerosol dispensing system, the use of a relatively minor quantity of a neutral propellant in admixture with the product has greatly reduced the problem of flammability that occurred in conventional aerosol systems when the propellant was a hydrocarbon. In such prior systems, the use of a relatively large quantity of a hydrocarbon propellant as required for a relatively thick or viscous product, could produce an aerosol spray that was highly flammable due to the concentration levels of hydrocarbon propellant within the spray. In my dispensing system, the neutral propellant which is discharged with the product is present in a relatively minor amount as compared with the amount of propellant employed in previous aerosol systems. Thus, when the neutral propellant is a hydrocarbon propellant, the concentration of hydrocarbon propellant in the aerosol spray is greatly reduced so that the spray itself may be much less flammable than the spray from prior aerosol systems utilizing a hydrocarbon propellant.
By the same token, toxicity problems which characterized prior conventional aerosol systems have been largely eliminated with my aerosol dispensing system since the quantity of neutral propellant that is discharged with the product is markedly reduced from the amount of propellant that was discharged during usage of previous aerosol systems. This advantage of my aerosol dispensing system is of particular importance in view of the increasing evidence that fluorocarbon propellants may pose a grave environmental hazard by reducing the ozone layer which surrounds the earth and which acts to absorb harmful solar radiation. In my aerosol dispensing system, the neutral propellant need not be a fluorocarbon propellant as was previously required in many conventional aerosol systems to avoid the problems of flammability and product incompatibility which characterized the use of hydrocarbon propellants. Thus, in my aerosol dispensing system, the neutral propellant which is discharged with the product may be completely non-toxic in addition to being discharged in only a relatively small quantity during use of the aerosol dispensing system.
As described in my prior copending U.S. application Ser. No. 544,390, a somewhat larger amount of a neutral propellant has been generally required in aerosol dispensing systems having a finely divided powder product than was required for aerosol dispensing systems in which the product has been a relatively non-foaming liquid. In systems where the product has been a finely divided powder, it was necessary that the neutral propellant be present in a sufficient amount to form a slurry with the product such that the product would have flow characteristics which assure its flow to the spray head during discharge of the product. In the case of a relatively non-foaming liquid product, a lesser quantity of neutral propellant could be utilized while providing suitable flow characteristics to the product which permitted it to flow to the spray head during discharge of the product.